Absolutely love this scene in this movie and played in over so many times but was always unsure on exactly what McCall was trying get across to Teddy with that story. So I Goggle searched and came here and read everyone’s comments and then watched that scene again twice… and now I get it.
Before McCall tells the story Teddy asks him, “When you look at me… what do you see? Hm? The answer’s nothing. I have no feelings about you one way or the other. You’re like… like lint or a bottle cap. You’re just a thing to remove.”
In the middle of the story McCall says three very important things: He tells Teddy to stop him if he knows the story [Teddy says, “Oh no. Carry on”] and he says “Intruders” (plural) broke into the home and some small things were stolen, things a “child” (singular) might steal.
Then after McCall tells the story Teddy says “It’s a well know story contradicting his “Oh no. Carry on” when McCall asked him if he knows the story. Then McCall says he thinks the boy killed the couple who took him in because he couldn’t bear the thought of being thrown away like a piece of lint or a bottle cap… so, “He decided not to find out”
I think the story is just a parable for McCall to convey to Teddy that before he would be disposed of like a piece of lint or a bottle cap, that he would kill Teddy.